Solid ink or phase change ink printers conventionally use ink in a solid form, either as pellets or as ink sticks of colored cyan, yellow, magenta and black ink, that are inserted into feed channels through openings to the channels. Each of the openings may be constructed to accept sticks of only one particular configuration. Constructing the feed channel openings in this manner helps reduce the risk of an ink stick having a particular characteristic being inserted into the wrong channel. After the ink sticks are fed into their corresponding feed channels, they are urged by gravity or a mechanical actuator to a heater assembly of the printer. The heater assembly includes a heater that converts electrical energy into heating a melt plate. The melt plate is typically formed from aluminum or other lightweight material in the shape of a plate or an open sided funnel. The heater is proximate to the melt plate to heat the melt plate to a temperature that melts an ink stick coming into contact with the melt plate. The melt plate may be tilted with respect to the solid ink channel so that as the solid ink impinging on the melt plate changes phase, it is directed to drip into the reservoir for that color. The ink stored in the reservoir continues to be heated while awaiting subsequent use.
Each reservoir of colored, liquid ink may be coupled to a print head through at least one manifold pathway. As used herein, liquid ink refers to ink that is in a liquid state, such as melted solid ink or aqueous ink. Melted solid ink refers to ink that is in a solid state at typical room temperatures and that has been heated so it changes to a molten state and remains so when elevated above ambient temperature. The liquid ink is pulled from the reservoir as the printhead demands ink for jetting onto a receiving medium or image drum. The printhead elements, which are typically piezoelectric devices, receive the liquid ink and expel the ink onto an imaging surface as a controller selectively activates the elements with a driving voltage. Specifically, the liquid ink flows from the reservoirs through manifolds to be ejected from microscopic orifices by piezoelectric elements in the print head.
Printers having multiple print heads are known. The print heads in these printers may be arranged so a print head need not traverse the entire width of a page during a printing operation. The print heads may also be arranged so multiple rows may be printed in a single operation. Each print head, however, may need to receive multiple colors of ink in order to print the image portion allotted to the print head.
While independent conduit lines may be used to couple each melted ink reservoir to each of the print heads, such a configuration is very inefficient for routing and retention. Actual distances between the reservoirs and heads are much longer. Also, some conduit lines may be sufficiently long that under some environmental conditions the ink may solidify before it reaches its target print head. Conduits must be flexibly configured and attached to one another to allow relative motion for printer operation and reasonable service access. To address these and other issues, an ink umbilical assembly has been developed. Umbilical assembly refers to a plurality of conduit groupings that are assembled together and may be in association with a heater to maintain the ink in each plurality of conduits at a temperature different than the ambient temperature. The term conduit refers to a body having a passageway through it for the transport of a liquid or a gas. The umbilical assembly is flexible enough to enable relative movement between adjacent print heads and between print heads and reservoirs.
A set of conduits may be comprised of independent conduits that are coupled together at each end of the conduits so the conduits are generally parallel to one another along the length of the ink umbilical. Alternatively, the conduits may be extruded in a single structure. A heater may be positioned adjacent to the ink umbilical to transfer heat into the conduits of the umbilical. All of the outlet ends of a set of conduits may be coupled to the same print head. Each conduit in each set of conduits is coupled at an inlet end to an ink source or reservoir and at an outlet end to a print head. Thus, the ink conduit lines remain grouped up to the point where they connect to a printhead to help maintain thermal efficiency. Each conduit may carry ink of a different color. As used herein, coupling refers to both direct and indirect connections between components.
A block diagram for an umbilical system that couples four melted ink reservoirs to four printheads in a solid ink printer is shown in FIG. 7. The system 10 includes reservoirs 14A, 14B, 14C, and 14D that are coupled to print heads 18A, 18B, 18C, and 18D through staging areas 16A1-4, 16B1-4, 16C1-4, and 16D1-4, respectively. Each reservoir collects melted ink for a single color. As shown in FIG. 4, reservoir 14A contains cyan colored ink, reservoir 14B contains magenta colored ink, reservoir 14C contains yellow colored ink, and reservoir 14D contains black colored ink. FIG. 4 shows that each reservoir is coupled to each of the print heads to deliver the colored ink stored in each reservoir. Consequently, each print head receives each of the four colors: black, cyan, magenta, and yellow, although other colors may be used for other types of color printers. The melted ink is held in the high pressure staging areas where it resides until a print head requests additional ink. The spatial relationship between reservoirs and print heads are shown in close proximity in the schematic such that the run length of parallel grouping is not illustrated.
From time to time and for various reasons, ink needs to be removed from a printhead. To accomplish this task, an air source may be coupled to a printhead to push air into the ink passageways within the printhead and expel ink through the nozzles for collection in a drip pan or the like. Because the passageways in the printhead are small, the air needs to be filtered to remove debris and dust from the air that may be sufficient to block or partially block an ink passageway in the printhead. In previously known printheads, the filter was located within the printhead. Sometimes, printheads are overfilled with ink and the ink backs up to a position that wets the filter media within the printhead. Unfortunately, this wetting degrades the ability to pressurize the printhead for purging as well as the air venting for the printhead. The impaired air filter cannot be remedied without replacing the entire printhead. Consequently, a more easily serviced air filter would be useful for printhead maintenance.